Detecting the Stochastic Gravitational Wave Background from Primordial Black Holes in Slow-reheating Scenarios

TL;DR

This paper investigates how a slow-reheating phase after inflation can produce a stochastic gravitational wave background through primordial black hole formation and related structures, potentially detectable by gravitational wave observatories.

Contribution

It models the SGWB from primordial black holes formed during slow-reheating with an enhanced primordial power spectrum, linking PBH dark matter to gravitational wave signals.

Findings

SGWB from PBH formation during slow-reheating can be within detection range.

Enhanced primordial power spectrum is necessary for PBH formation of dark matter.

Predicted gravitational wave signals depend on the PBH mass and reheating dynamics.

Abstract

After primordial inflation, the universe may have experienced a prolonged reheating epoch, potentially leading to a phase of matter domination supported by the oscillating inflaton field. During such an epoch, perturbations in the inflaton virialize upon reentering the cosmological horizon, forming inflaton structures. If the primordial overdensities are sufficiently large, these structures collapse to form primordial black holes (PBHs). To occur at a significant rate, this process requires an enhanced primordial power spectrum (PPS) at small scales. The enhancement of the PPS, as well as the formation and tidal interaction of the primordial structures, will in turn source a stochastic gravitational wave background(SGWB) that could be detected by current and/or future gravitational wave detectors. In this paper, we study the SGWB arising from these different sources during slow-reheating, focusing on a PPS that satisfies the requirements necessary for the formation of PBHs with a mass of $M_{\rm PBH}\simeq 10^{21}$ and that constitute the entirety of dark matter in the universe.